JP2017184788A - Scanning laser ophthalmoscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To acquire a front image of the ocular fundus appropriately.SOLUTION: An SLO 1 includes: an irradiation optical system 10 having a light source 11, a scanning part 16 for scanning a laser beam emitted from the light source 11 on the ocular fundus Er, and an objective lens system 17 disposed between an eye E to be examined and the scanning part 16 for forming a turning point P of the laser beam guided from the scanning part 16; and a light receiving optical system 20 that shares the objective lens system 17 with the irradiation optical system 10 and includes a light receiving element for receiving light from the ocular fundus Er accompanying the irradiation of the laser beam. The objective lens system 17 includes a first lens system 17a for bending the laser beam toward the turning point P, and a second lens system 17b disposed between the first lens system 17a and the scanning part 16. The second lens system 17b has an inclined lens disposed inclined with respect to an optical axis L1. The lens surface on the light source side in the inclined lens has a larger curvature radius than the lens surface on the light source side in the first lens system 17a.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to a scanning laser ophthalmoscope that captures a front image of the fundus of a subject's eye.

  Conventionally, a scanning laser ophthalmoscope is known as an apparatus that captures a front image of the fundus of a subject's eye. This type of device is provided with an opening (confocal stop) at the fundus conjugate position in front of the light receiving element to which light from the fundus is incident, and noise light is prevented from entering the light receiving element. The For example, Patent Document 1 discloses an apparatus in which a lens system (refractive system) is applied to an objective optical system.

JP 2016-28687 A

  Here, in an apparatus in which a lens system is applied to the objective optical system, if a fundus image is obtained with a larger angle of view, reflection on the lens surface of the objective optical system cannot be completely removed by the confocal stop, and the light receiving element It was confirmed that the incident light is easy to enter.

  The present disclosure has been made in view of the above-described problems of the prior art, and an object of the present disclosure is to provide a scanning laser ophthalmoscope that can favorably obtain a front image of the fundus.

  The scanning laser ophthalmoscope according to the first aspect of the present disclosure includes a light source, a scanning unit for scanning laser light emitted from the light source on the fundus of the eye to be examined, and between the eye to be examined and the scanning unit. And an objective lens system that forms a turning point at which the laser beam guided from the scanning unit is rotated in accordance with the operation of the scanning unit, and the objective lens system to the irradiation optical A scanning laser ophthalmoscope including a light receiving optical system having a light receiving element that receives light from the fundus accompanied with irradiation of the laser light, and the objective lens system includes the laser light A first lens system for bending the lens toward the turning point, and a second lens system disposed between the first lens system and the scanning unit, the second lens system including the irradiation Tilted with respect to the optical axis of the optical system It has arranged the tilted lens, the lens surface of the light source side in the inclined lenses than the lens surface of the light source side in the first lens system having a large radius of curvature.

  A scanning laser ophthalmoscope according to a second aspect of the present disclosure includes a light source, a scanning unit for scanning laser light emitted from the light source on the fundus of the eye to be examined, and between the eye to be examined and the scanning unit. And an objective lens system that forms a turning point at which the laser beam guided from the scanning unit is rotated in accordance with the operation of the scanning unit, and the objective lens system to the irradiation optical And a light receiving optical system having a light receiving element for receiving light from the fundus upon irradiation with the laser light, wherein the scanning units are at different positions. The objective lens system includes two optical scanners arranged and having different scanning directions of the laser light, and the objective lens system includes a first lens system for bending the laser light toward the turning point, and the first lens system And said running A second lens system disposed between the first lens unit and the second lens system, wherein the second lens system includes a tilt lens that is tilted with respect to the optical axis of the irradiation optical system, and the tilt lens is The optical axis of the irradiation optical system is arranged so as to cancel out the astigmatic difference at the turning point caused by the two optical scanners.

  According to the present disclosure, a front image of the fundus can be obtained favorably.

It is a figure which shows the external appearance of SLO in this embodiment. It is a figure which shows the optical system in the main-body part of SLO. It is the figure which showed an example of the aperture unit applicable instead of the confocal stop shown in FIG. It is the figure which showed typically the light beam of the laser beam in the periphery of a scanning part. It is the figure which showed the objective lens system which concerns on a comparative example. It is a figure which shows the optical system in the state which mounted | wore with the lens attachment. It is a figure which shows the detailed structure of a light-shielding member. FIG. 3 is a diagram for explaining noise light shielded by a light shielding member in the optical system shown in FIG. 2. It is a figure which shows an example of the control system in SLO. It is the flowchart which showed the outline | summary of imaging | photography operation | movement in SLO. It is the figure which showed the picked-up image (reflection image) of the fundus by SLO. It is the figure which showed the background image corresponding to FIG. FIG. 13 is a diagram illustrating a difference image between the fundus image in FIG. 11 and the background image in FIG. 12. It is a figure for demonstrating a partial background image, and has shown the area | region extracted as a partial background image from the background image of FIG. FIG. 15 is a diagram illustrating a difference image between the fundus image in FIG. 11 and the partial background image in FIG. 14.

  Hereinafter, a scanning laser opthalmoscope (SLO) according to an exemplary embodiment of the present disclosure will be described with reference to the drawings. A scanning laser ophthalmoscope (hereinafter, referred to as “SLO”) 1 according to the present disclosure scans a laser beam on the fundus and acquires a front image of the fundus by receiving a return beam of the laser beam from the fundus. It is. As an SLO1 imaging method, in addition to an imaging method using fundus reflection light, for example, a fluorescence imaging method is known. The scanning laser ophthalmoscope according to the present disclosure may be an apparatus integrated with another ophthalmologic apparatus such as an optical coherence tomography (OCT) or a perimeter.

  In the embodiment described below, unless otherwise specified, the SLO 1 scans the fundus image by two-dimensionally scanning the laser light focused on the spot on the observation surface based on the operation of the scanning unit. Shall be obtained. However, it is not necessarily limited to this. For example, the technique of the present disclosure may be applied to a so-called line scan SLO. In this case, the line-shaped laser beam is scanned one-dimensionally on the observation surface based on the operation of the scanning unit.

<Appearance of the device>
First, a schematic configuration of a scanning laser opthalmoscope (SLO: Scanning Laser Optoscope) 1 according to the present embodiment will be described with reference to FIG. As shown in FIG. 1, the SLO 1 includes a main body (device main body) 2 and a wide-angle lens attachment 3 (hereinafter abbreviated as “lens attachment 3”). In the present embodiment, the main body 2 includes a main optical system (see FIG. 2) and a control system (see FIG. 9) when the SLO 1 captures a fundus image. Moreover, in this embodiment, the lens attachment 3 is comprised so that attachment or detachment with respect to the housing | casing 2a of the main-body part 2 is possible. More specifically, the lens attachment 3 is attached to and detached from the subject-side housing surface. The SLO 1 is capable of photographing the fundus oculi when the lens attachment 3 is attached and when it is not attached. The lens attachment 3 is attached to the housing 2 a to widen the imaging angle of view of the fundus image obtained by the main body 2.

  In the present embodiment, the main body 2 includes a measurement unit 4, an alignment mechanism 5, a base 6, a face support unit 7, and a sensor 8. The measuring unit 4 stores an optical system for imaging the eye E. This optical system will be described later with reference to FIG.

  The alignment mechanism 5 is used for aligning the apparatus with respect to the eye E. The alignment mechanism 5 of the present embodiment moves the measurement unit 4 three-dimensionally with respect to the base 6. That is, they are moved in the Y direction (up and down direction), the X direction (left and right direction), and the Z direction (front and back direction).

  As shown in FIG. 1, the face support unit 7 supports the face of the subject with the eye E to be measured facing the measurement unit 4. In the present embodiment, the face support unit 7 is provided on the base 6.

  The sensor 8 is a detection unit that detects the mounting of the lens attachment 3. The sensor 8 outputs an electrical signal corresponding to the mounting state of the lens attachment 3. For example, the sensor 8 continuously outputs electrical signals having different voltage values when the lens attachment 3 is attached to the main body 2 and when the lens attachment 3 is not attached to the main body 2. There may be. Such a sensor 3 may be a contact sensor such as a microswitch, or may be a non-contact sensor such as a photoelectric sensor or a magnetic sensor.

<Optical configuration on the main unit>
Next, an optical system provided in the main body 2 of the SLO 1 will be described. As shown in FIG. 2, the SLO 1 includes an irradiation optical system 10 and a light receiving optical system 20 (collectively referred to as “imaging optical system”). That is, the irradiation optical system 10 and the light receiving optical system 20 are housed in the same housing 2a. The SLO 1 takes a fundus image using these optical systems 10 and 20.

  The irradiation optical system 10 includes at least a scanning unit 16 and an objective lens system 17. 2, the irradiation optical system 10 further includes a laser beam emitting unit 11, a collimating lens 12, a perforated mirror 13, and a lens 14 (in this embodiment, a part of the diopter adjusting unit 40). ) And the lens 15.

  The laser beam emitting unit 11 is a light source of the irradiation optical system 10. The laser beam emitting unit 11 may include, for example, a laser diode (LD) and a super luminescent diode (SLD). Although a description of a specific structure is omitted, the laser beam emitting unit 11 emits light in at least one wavelength region. In the present embodiment, light of a plurality of colors is emitted from the laser light emitting unit 11 simultaneously or selectively. For example, in the present embodiment, a total of four colors of light of three colors in the visible range of blue, green, and red and one color in the infrared range are emitted from the laser beam emitting unit 11. Three colors in the visible range of blue, green, and red are used for color photography, for example. For example, color photography is performed by emitting three colors of blue, green, and red from the light source 11 substantially simultaneously. In addition, any one of the three colors in the visible range may be used for visible fluorescent photographing. For example, blue light may be used for FAG imaging (fluorescein fluorescence contrast imaging), which is a type of visible fluorescence imaging. In addition, for example, infrared light may be used for infrared fluorescent photographing as well as infrared photographing using infrared fundus reflected light. For example, ICG imaging (indocyanine green fluorescence imaging) is known as infrared fluorescence imaging. In this case, the infrared light emitted from the laser light source 11 is preferably set in a wavelength range different from the fluorescence wavelength of indocyanine green used in ICG imaging.

  The laser beam is guided to the fundus oculi Er along the path of the light beam shown in FIG. That is, the laser light from the laser light emitting unit 11 passes through the collimating lens 12, the opening formed in the perforated mirror 13, passes through the lens 14 and the lens 15, and then proceeds to the scanning unit 16. The laser light reflected by the scanning unit 16 passes through the objective lens system 17 and is then applied to the fundus Er of the eye E. As a result, the laser light is reflected and scattered by the fundus Er. Alternatively, a fluorescent substance existing in the fundus is excited to generate fluorescence from the fundus. These lights (that is, reflected / scattered light, fluorescence, etc.) are emitted from the pupil as return light.

  In the present embodiment, the lens 14 shown in FIG. 2 is a part of the diopter adjustment unit 40. The diopter adjustment unit 40 is used to correct (reduce) the diopter error of the eye E. For example, the lens 14 can be moved in the optical axis direction of the irradiation optical system 10 by the drive mechanism 14a. Depending on the position of the lens 14, the diopter of the irradiation optical system 10 and the light receiving optical system 20 changes. For this reason, by adjusting the position of the lens 14, the diopter error of the eye E to be examined is reduced. As a result, the condensing position of the laser light is applied to the observation site (for example, the retina surface) of the fundus Er. It can be set. Note that the diopter adjusting unit 40 may be applied with an optical system different from that shown in FIG. 2, such as a Badar optical system.

  The scanning unit 16 (also referred to as “optical scanner”) is a unit for scanning the fundus with laser light emitted from a light source (laser light emitting unit 11). In the following description, it is assumed that the scanning unit 16 includes two optical scanners having different scanning directions of laser light unless otherwise specified. These two optical scanners are arranged at different positions. That is, an optical scanner 16a for main scanning (for example, scanning in the X direction) and an optical scanner 16b for sub-scanning (for example, scanning in the Y direction) are included. The optical scanner 16a for main scanning and the optical scanner 16b for sub scanning may be a resonant scanner and a galvanometer mirror, respectively. However, the present invention is not necessarily limited to this. For each of the optical scanners 16a and 16b, other light reflecting mirrors (galvano mirrors, polygon mirrors, resonant scanners, MEMS, etc.) and the light traveling (deflection) direction are changed. An acousto-optic device (AOM) or the like may be applied. The scanning unit 16 is not necessarily a plurality of optical scanners, and may be a single optical scanner. As a single optical scanner that scans laser light two-dimensionally, for example, an optical scanner using either a MEMS device or an acousto-optic element (AOM) has been proposed.

  The objective lens system 17 is an objective optical system of SLO1. The objective lens system 17 is used to guide the laser beam scanned by the scanning unit 16 to the fundus oculi Er. For this purpose, the objective lens system 17 forms a turning point P around which the laser light passed through the scanning unit 16 is turned. The turning point P is formed on the optical axis L 1 of the irradiation optical system 10 and at a position optically conjugate with the scanning unit 16 with respect to the objective lens system 17. The detailed configuration of the objective lens system 17 will be described later. In the present disclosure, “conjugate” is not necessarily limited to a complete conjugate relationship, and includes “substantially conjugate”. In other words, the case where the fundus image is arranged so as to deviate from the complete conjugate position within the range allowed in relation to the purpose of use of the fundus image (for example, observation, analysis, etc.) is also included in “conjugate” in the present disclosure.

  The laser light that has passed through the scanning unit 16 passes through the objective lens system 17 and is irradiated to the fundus Er through the turning point P. For this reason, the laser light that has passed through the objective lens system 17 is turned around the turning point P as the scanning unit 16 operates. As a result, in the present embodiment, laser light is scanned two-dimensionally on the fundus Er. The laser light applied to the fundus Er is reflected at a condensing position (for example, the retina surface). Further, the laser light is scattered by the tissues before and after the condensing position. The reflected light and scattered light are each emitted from the pupil as parallel light.

  Next, the light receiving optical system 20 will be described. The light receiving optical system 20 shares the objective lens system 17 with the irradiation optical system 10 and has at least one light receiving element. For example, as shown in FIG. 2, you may have several light receiving element 25,27,29. In this case, light from the fundus Er due to the laser light irradiated by the irradiation optical system 10 is received by the light receiving elements 25, 27, and 29.

  As shown in FIG. 2, the light receiving optical system 20 in the present embodiment may share the members arranged from the objective lens system 17 to the perforated mirror 13 with the irradiation optical system 10. In this case, the light from the fundus is guided back to the aperture mirror (optical path branching member in the present embodiment) 13 along the optical path of the irradiation optical system 10. Moreover, the perforated mirror 13 branches the irradiation optical system 10 and the light receiving optical system 20. In the present embodiment, the light from the fundus Er is reflected by the reflecting surface of the perforated mirror 13 and guided to the independent optical path of the light receiving optical system 20 (light path on the light receiving elements 25, 27, and 29 side). The light traveling from the common optical path of the irradiation optical system 10 and the light receiving optical system 20 to the perforated mirror is likely to contain noise light in a region in the vicinity of the optical axis L2 in the principal ray of the laser light. Note that the noise light referred to here mainly refers to light from other than the target of photographing and observation, such as the condensing position of the fundus Er (for example, the retina surface). Specifically, the light reflected by the cornea, the light reflected from the optical system inside the apparatus, and the like can be mentioned. The perforated mirror 13 guides the light from the fundus Er to the independent optical path of the light receiving optical system 20 while removing at least a part of such noise light. In the present embodiment, the perforated mirror 13 is disposed at a conjugate position with the anterior segment. For this reason, the reflected light from the cornea, the reflected light from the optical system inside the apparatus, and the like are removed by the opening of the perforated mirror 13. On the other hand, of the light from the fundus Er, the light that passes around the pupil is reflected by the reflecting surface of the perforated mirror 13 and guided to the independent optical path.

  The optical path branching member that branches the irradiation optical system 10 and the light receiving optical system 20 is not limited to the perforated mirror 13. For example, instead of the perforated mirror 13, a member obtained by replacing the aperture and the reflecting surface of the perforated mirror 13 with each other can be used as the optical path branching portion. However, for example, when applied to FIG. 2, the independent optical path of the irradiation optical system 10 (from the light source 11 to the perforated mirror 13) and the independent optical path of the light receiving optical system 20 (from the perforated mirror 13 to the light receiving element 25, 27 and 29) must be replaced with each other. The optical path branching member may be another beam splitter.

  The light receiving optical system 20 includes a lens 21, a light blocking unit 22, a pinhole plate 23, and a light separating unit (light separating unit) 30 in the reflected light path of the perforated mirror 13. In addition, lenses 24, 26, and 28 are provided between the light separation unit 30 and the light receiving elements 25, 27, and 29.

  Although details will be described later, the light shielding unit 22 shields light in the vicinity of the optical axis L <b> 2 of the light receiving optical system 20. The light from the fundus conjugate plane passes through the light shielding unit 22, and at least a part of the noise light is shielded by the light shielding unit 22.

  The pinhole plate 23 is disposed on the fundus conjugate plane and functions as a confocal stop in the SLO1. That is, when the diopter is appropriately corrected by the diopter adjustment unit 40, the light from the fundus Er that has passed through the lens 21 is focused at the opening of the pinhole plate 23. The pinhole plate 23 removes light from a position other than the condensing point (or focal plane) of the fundus Er, and the remainder (light from the condensing point) is mainly guided to the light receiving elements 25, 27, and 29. .

  Unless otherwise specified, the description will be made assuming that a pinhole plate 23 (confocal stop) is placed at the fundus conjugate position between the light receiving elements 25, 27, 29 and the perforated mirror 13. Instead of the pinhole plate 23, an aperture unit 230 as shown in FIG. 3 may be arranged. The aperture unit 230 has a confocal stop 231 having an opening at a position conjugate with the condensing point on the observation surface (fundus) and a light-shielding portion at a position conjugate with the condensing point on the observation surface (fundus). Of apertures 232 and 232 having openings for allowing light in a region away from the optical axis L2 to pass through the light receiving elements 25, 27, and 29 among the light scattered before and after Deploy. When the apertures 232 and 232 are arranged, a fundus image is obtained by scattered light from before and after the condensing point. In this case, a minute biological material in the fundus that cannot be confirmed in a fundus image (for example, a reflection image) captured when the confocal stop 231 is disposed can be imaged.

  The light separation unit 30 separates light from the fundus Er. In the present embodiment, the light from the fundus Er is light-selectively separated by the light separation unit 30. The light separation unit 30 may also serve as a light branching unit that branches the optical path of the light receiving optical system 20. For example, as illustrated in FIG. 2, the light separation unit 30 may include two dichroic mirrors (dichroic filters) 31 and 32 having different light separation characteristics (wavelength separation characteristics). The optical path of the light receiving optical system 20 is branched into three by the two dichroic mirrors 31 and 32. Further, one of the light receiving elements 25, 27, and 29 is disposed at the tip of each branch optical path.

  For example, the light separation unit 30 separates the wavelength of light from the fundus Er and causes the three light receiving elements 25, 27, and 29 to receive light in different wavelength ranges. For example, the light receiving elements 25, 27, and 29 may receive light of three colors of blue, green, and red one by one. In this case, a color image can be easily obtained from the light reception results of the light receiving elements 25, 27, and 29.

  In addition, the light separation unit 30 may cause at least one of the light receiving elements 25, 27, and 29 to receive infrared light used in infrared imaging. In this case, for example, fluorescence used in fluorescence imaging and infrared light used in infrared imaging may be received by different light receiving elements.

  The wavelength bands in which the light receiving elements 25, 27, and 29 have sensitivity may be different from each other. In addition, at least two of the light receiving elements 25, 27, and 29 may have sensitivity in a common wavelength range. Each of the light receiving elements 25, 27, 29 outputs a signal corresponding to the intensity of the received light (hereinafter referred to as a light receiving signal). In the present embodiment, the light reception signal is processed separately for each light receiving element to generate an image. That is, in this embodiment, a maximum of three types of fundus images are generated in parallel.

  In SLO1 (here, the optical system of the main body 2), the anterior ocular conjugate position between the perforated mirror 13 and the objective lens system 17 is 2 between the position of the scanning unit 16 and the position of the perforated mirror 13. It is formed only in places. Thereby, an optical system with a short overall length is realized.

<Conditions for optical scanner arrangement interval>
If the laser light applied to the fundus is vignetted by the pupil, a fundus image with a dark surrounding is obtained. On the other hand, vignetting can be suppressed by setting the distance a between the optical scanner 16a and the optical scanner 16b so as to satisfy the following formula (1).

a ≤ {sin (θ / 2) / sin (θo / 2)} · (k-1) · φ / tan (θo / 2) (1)
Here, θ is an angle representing the field diameter, θo is the full angle of the optical swing angle in the scanning unit 16 (optical scanners 16a and 16b), and φ is the opening of the aperture mirror 13 in the anterior segment. The diameter of the image. K is a constant obtained as a result of the inventor's examination. k is a value larger than 1. As a result of the inventor's investigation, it has been confirmed that when the constant k is set to a value of about “1.5”, vignetting hardly occurs even when other parameters are changed.

  For example, when θ = 60 °, θo = 16 °, φ = 1.4 mm, and k = 1.5, if a is within 18 mm, the laser beam passes closer to the turning point P. For example, even with an eye having a small pupil diameter of about φ2.5 mm, the laser beam is less likely to be vignetted.

  Formula (1) is demonstrated using FIG. FIG. 4 is a diagram schematically showing the periphery of the scanning unit 16. FIG. 4 schematically shows the light flux at the time of projection passing through the perforated mirror 13. G is an intermediate point between the optical scanners 16a and 16b and is formed at a position that is an anterior eye conjugate (pupil conjugate). The thickness of the light beam when the optical scanners 16a and 16b are stationary (actual light beam thickness) is denoted by Do. Further, the apparent thickness of the laser beam at the intermediate point C (intermediate surface) during the operation of the optical scanners 16a and 16b is indicated as D.

  Here, “sin (θ / 2) / sin (θo / 2)” in Equation (1) is considered to be a term representing the magnification in the objective lens system 17 based on the assumption of the sine condition. Therefore, “sin (θ / 2) / sin (θo / 2) · φ” included in the equation (1) is synonymous with the actual thickness Do of the light flux. Here, Formula (1) is rewritten using Do, and is shown as the following Formula (2).

a ≤ Do ・ (k-1) / tan (θo / 2)
a ・ tan (θo / 2) ≦ Do ・ (k-1) (2)
As is apparent from FIG. 4, the relationship “D = Do + a · tan (θo / 2)” is established. Therefore, when (2) is replaced and rearranged, Equation (3) can be derived.

D = Do + a · tan (θo / 2) ≤ Do · k (3)
Thus, Equation (1) is a condition that defines that the apparent light beam thickness D at the intermediate point C, which is the anterior segment conjugate position, is within k times the actual light beam thickness Do. Become. Setting the constant k as a value of about “1.5” has been confirmed by the inventor as a value that makes it difficult for vignetting to actually occur, paying attention to this relationship.

<Optical configuration contributing to noise suppression>
As described above, the SLO 1 of the present embodiment can suppress noise light from being incident on the light receiving elements 25, 27, and 29 by the confocal stop (pinhole plate 23) and the perforated mirror 13.

  However, in general, in an SLO having an objective lens system, it is difficult to secure the focal length of the objective lens system with a margin if an attempt is made to secure a shooting angle of view of several tens of degrees or more. At this time, the light source side lens surface of the lens that bends the laser beam greatly in the objective lens system is arranged near the fundus conjugate plane (also referred to as the intermediate image plane) related to the objective lens system, so that the confocal stop and the hole are opened. Noise light that cannot be removed by a mirror or the like is likely to be generated. In a lens that bends laser light greatly, the radius of curvature of the lens surface on the light source side tends to be small. For this reason, even if this lens is tilted, it is difficult to escape noise light out of the light receiving optical path. The fundus conjugate plane related to the objective lens system is a primary enlarged image formed by the objective lens system, and mainly refers to an inverted image. However, the primary enlarged image is not necessarily required.

  In addition, diopter correction may be performed in order to properly focus laser light on the fundus. At this time, the fundus conjugate plane formed through the objective lens system moves according to the diopter correction amount. For example, the stronger the myopia of the eye to be examined, the closer the fundus conjugate plane related to the objective lens system is to the eye E side as a result of diopter correction. Therefore, it is conceivable that noise light that cannot be removed by a confocal stop, a perforated mirror, or the like is generated even under the influence of diopter correction.

  On the other hand, SLO1 of this embodiment may have the structure described below. Note that when implementing the technology according to the present disclosure, the configurations described below are not necessarily all implemented, and some may be selectively implemented.

<Objective lens system>
As shown in FIG. 2, the objective lens system 17 includes a first lens system 17a and a second lens system 17b. Each lens system 17a, 17b includes at least one lens. The first lens system 17a is a main lens system for bending the laser light toward the turning point in the objective lens system 17. For example, the first lens system 17a shown in FIG. 2 bends the laser light toward the turning point P at the position where the chief ray height of the laser light in the objective lens system 17 is highest. In addition, the first lens system 17 a is disposed closest to the eye to be examined in the objective lens system 17.

  In the present embodiment, the first lens system 17a is formed by one lens 171. As shown in FIG. 2, an aspheric lens may be used as the lens 171.

  By the way, in order to realize fundus imaging at an angle of view of several tens of degrees or more while ensuring a sufficient working distance between the apparatus and the eye E, as shown in FIG. Is provided in the first lens system 17a, and it is necessary to bend the laser beam. For this reason, in the objective lens system 17 (particularly, the first lens system 17a), aberrations (for example, spherical aberration, coma aberration, etc.) depending on the lens diameter are likely to occur. On the other hand, the lens 171 desirably has a lens surface formed in an aspherical shape so as to reduce aberration depending on the aperture of the lens. For example, the lens 171 has an aspheric lens surface so as to reduce the spherical aberration of the image formed at the turning point P. For example, the lens surface 171a on the light source side of the lens 171 may be an aspherical surface. For example, the lens surface 171a may be formed by a curved surface having a radius of curvature that increases as the position is away from the optical axis (lens axis) of the lens 171. On the other hand, the lens surface 171b on the eye side of the lens 171 may be a spherical surface, a flat surface, or an aspherical surface.

  The lens 171 (or the first lens system 17a) is preferably arranged so that its optical axis is along the optical axis L1 of the irradiation optical system 10. For example, since the lens 171 is a lens having a large refractive power, the distortion in the fundus image can be suppressed by arranging the lens 171 along the optical axis L1. Here, the optical axis of the lens 171 may be completely coaxial with the optical axis L1 of the irradiation optical system 10, or may be slightly inclined with respect to the optical axis L1. For example, the optical axis L1 of the lens 171 may be slightly tilted within a range where distortion of the fundus image is allowed. By arranging the optical axis of the lens 171 so as to be inclined with respect to the optical axis L1, the inclination of the image plane derived from an “inclined lens” described later may be reduced.

  The second lens system 17 b is disposed between the first lens system 17 a and the scanning unit 16. The second lens system 17b has at least one lens whose lens surface on the light source side is inclined with respect to the optical axis L1 of the irradiation optical system 10 (in the following description, referred to as an “inclined lens” for convenience). When the second lens system 17b includes a plurality of lenses, two or more lenses may be tilted lenses, or all may be tilted lenses as shown in FIG.

  For example, in the present embodiment, each of the cemented lens 172 and the convex meniscus lens 173 is an inclined lens in the second lens system 17b. As shown in FIG. 2, in each of the inclined lenses 172 and 173, the lens surfaces 172 a and 173 a on the light source side are formed to have a larger radius of curvature than the lens surface 171 a on the light source side in the first lens system 17. Yes. Each of the inclined lenses 172 and 173 shown in FIG. 2 is a spherical lens. In addition, both tilt lenses 172 and 173 have positive power. However, the present invention is not necessarily limited thereto, and an aspherical lens and / or a lens having negative power may be applied to a part or all of the lenses included in the second lens system 17b. .

  The second lens system 17b may include a lens for correcting the aberration generated by the first lens system 17a. For example, the cemented lens 172 of this embodiment corrects chromatic aberration. The corrected chromatic aberration may be one or both of axial chromatic aberration and lateral chromatic aberration. More specifically, the cemented lens 172 may be an achromatic lens formed by bonding at least two lenses having different light dispersion (Abbe number). Note that noise light may be generated by the reflection of the laser beam on the cemented surface 172b of the cemented lens 172. In contrast, the refractive indexes of the lenses included in the cemented lens 172 (concave lens and convex lens in FIG. 2) and the adhesive for bonding the lenses are the same (including substantially the same). Also good. Thereby, reflection of the laser beam at the joint surface 172b is suppressed. As a result, noise light due to reflection at the joint surface 172b is less likely to occur. Here, when the refractive index difference between each lens included in the cemented lens 172 and the adhesive is 0.01 or less, the effect of suppressing noise light is more suitably obtained.

  The cemented surface 172b of the cemented lens 171 is preferably convex toward the eye to be examined. This is because the joining surface 172b and the fundus conjugate surface H are separated from each other, so that generation of noise light is suitably suppressed.

  In addition, the higher the refractive index of each lens included in the cemented lens 172 and the adhesive, the easier it is to increase the radius of curvature of the cemented surface, and the reflected light on the cemented surface 172b is received by the light receiving elements 25, 27,. It becomes difficult to be reflected at an angle of incidence on 29. As a result, the influence of noise light on the fundus image is further suppressed. Moreover, the manufacturing cost of the cemented lens 172 can be suppressed by increasing the radius of curvature of the cemented surface 172b. For example, a concave lens and a convex lens that have a refractive index of approximately 1.63 and an adhesive for bonding the lenses may be selected.

  The number of lenses forming the cemented lens 172 may be determined according to the number of colors included in the laser light. For example, the two-piece cemented lens 172 can align the condensing position of two of the three colors included in the laser light with the condensing position of one other color. As described above, the SLO 1 of the present embodiment emits a total of four colors, that is, three colors of red, green, and blue, and one color in the infrared region, from the laser light emitting unit 11. In the case of a two-lens cemented lens 172 as shown in FIG. 2, the condensing position of blue light with the shortest wavelength and the condensing position of light in the infrared region are set to light having an intermediate wavelength ( The “intermediate wavelength” referred to here does not necessarily match the wavelength of the laser beam emitted from the laser beam emitting unit 11). It may be designed. By providing the cemented lens 172, the position of the turning point in the laser light of each color becomes difficult to shift. As a result, fundus imaging performed by projecting a plurality of colors of light can be favorably performed with a smaller pupil eye or with a larger angle of view.

  Each lens included in the cemented lens 172 may be selected so that the power of the cemented lens 172 becomes zero. In this case, the cemented lens 172 is unlikely to affect the inclination and height of the light beam. Therefore, the presence or absence of the cemented lens 172 hardly affects the design of the lens (for example, the first lens system 17a) that serves to bend the laser light in the objective lens system 17.

  The convex meniscus lens 173 has a positive power. This contributes to bending the laser beam to the turning point P. However, the bending amount is sufficiently smaller than that of the first lens system 17a.

  By the way, in order to secure the same angle of view as that of the present embodiment, a design solution in which a plurality of lenses included in the objective lens system as described above are formed as one cemented lens 500 is also conceivable (see FIG. See comparative example 5). However, when the objective lens system is formed by one cemented lens 500, the lens surface 500a is likely to be disposed near the fundus conjugate surface (intermediate image I). As a result, noise light is easily generated due to reflection of laser light on the lens surface 500a. Further, since the radius of curvature of the lens surface 500a on the light source side becomes small, it is difficult to escape the reflected light from the lens surface 500a from the light receiving optical path even if the lens 500 is tilted.

  In contrast to such a comparative example, the objective lens system 17 of the present embodiment is divided into a first lens system 17a and a second lens system 17b. Since the second lens system 17b is provided between the scanning unit 16 and the first lens system 17a, which is a main lens system for bending the laser light toward the turning point, the objective lens system 17 is compared. The lens surface 171a of the first lens system having a small radius of curvature can be easily arranged away from the fundus conjugate surface (intermediate image H) related to the objective lens system 17. As a result, the reflected light from the lens surface 171a is hardly incident on the light receiving elements 25, 27, and 29 as noise light. In addition, in the inclined lenses 172 and 173 of the second lens system 17b, the lens surfaces 172a and 173a that reflect the laser light are inclined with respect to the optical axis L1, and the lens surfaces 172a and 173a further include the first lens system. Since the lens surface 171a has a larger radius of curvature than the lens surface 171a, even if the position of any of the lens surfaces 172a and 173a is near the fundus conjugate surface (intermediate image H), the lens surfaces 172a and 173a The reflected light is unlikely to enter the light receiving elements 25, 27, and 29 as noise light. As a result, according to the objective lens system 17 of the present embodiment, noise light incident on the light receiving elements 25, 27, and 29 is hardly generated.

  Incidentally, as shown in FIG. 2, the fact that the optical scanner 16a for main scanning and the optical scanner 16b for sub-scanning are separate from each other in the image position of the scanning unit 16 in the pupil of the eye E to be examined. It can be a factor causing a point difference. In other words, the position of the turning point of the laser beam with respect to the main scanning direction and the position of the turning point of the laser light with respect to the sub-scanning direction can cause a shift in the direction along the optical axis L1. If there is an astigmatism difference, there is a high possibility that the laser beam will be vignetted at the pupil, so that unevenness in which the brightness at the peripheral part of the fundus image is darker than the central part is likely to occur.

  On the other hand, the inclined lenses 172 and 173 included in the second lens system 17b are inclined with respect to the optical axis L1 so that the astigmatic difference caused by the two optical scanners 16a and 16b is canceled (reduced). It may be arranged. In this case, the astigmatism difference caused by the tilt of the tilt lens and the astigmatism difference caused by the two optical scanners 16a and 16b cancel each other, so that the astigmatism remaining at the turning point P is suppressed. For example, as shown in FIG. 2, when the sub-scanning optical scanner 16 b and the main-scanning optical scanner 16 a are arranged in this order from the light source side, the tilt lens is appropriately set in the yz plane (in the paper plane). By ascending, the astigmatic difference can be reduced. As a result, a fundus image with uniform brightness can be easily obtained.

<Wide-angle lens attachment>
The SLO 1 is attached with the lens attachment 3. With reference to FIG. 6, the optical system in a state where the lens attachment 3 is mounted will be described.

  The lens attachment 3 is attached to the subject-side casing surface of the SLO 1 so that a second objective lens system 50 described later is disposed in the optical path of the laser light. For example, it is arranged near the first turning point P.

  As shown in FIG. 6, the lens attachment 3 mainly has a second objective lens system 50. In addition, the lens attachment 3 may have a lens system and a mirror system. For example, the lens attachment 3 shown in FIG. 6 has a diopter correction lens 57 (a diopter correction lens optical system). By attaching the lens attachment 3 to the SLO1, the optical system included in the lens attachment 3 is disposed between the objective lens system 17 of the SLO1 and the eye E to be examined.

  The diopter correction lens 57 cancels the diopter change caused by the second objective lens system 50 (that is, cancels part or all of the diopter change). More specifically, the diopter correction lens 57 suppresses a difference in diopter of light incident on the eye E between the lens attachment 3 attached state and the non-attached state. As shown in FIG. 6, the diopter correction lens 57 may be a lens having a positive power (more specifically, a plano-convex lens having a convex surface directed toward the eye E to be examined). It is assumed that the second objective lens system 50 has a refractive power of several tens of diopters or more when it is intended to realize fundus photographing at a wide angle (for example, an angle of view of φ90 ° or more) by mounting the lens attachment 3. . In this case, a case where the main body of the SLO1 (for example, the irradiation optical system 10) cannot correct the change in diopter can be considered. On the other hand, by applying a lens having a power corresponding to the second objective lens system 50 as the diopter correction lens 57, the diopter change due to the second objective lens system 50 is canceled out. As a result, a wide-angle fundus image can be favorably captured. Further, according to the diopter correction lens 57, since the difference in diopter of the light incident on the eye E between the lens attachment 3 attached state and the non-attached state is reduced, the lens attachment 3 can be attached to and detached from the SLO1. The accompanying diopter adjustment is simplified or no adjustment is required.

  Further, as shown in FIG. 6, the diopter correction lens 57 is arranged on the light source side with respect to the second objective lens system 50. More specifically, the diopter correction lens 57 is disposed at the position of the turning point P. As a result, the laser beam passes near the center of the diopter correction lens 57. Therefore, a small diameter lens can be used as the diopter correction lens 57. Further, since the laser light passes near the center of the diopter correction lens 57, the inclination of the chief ray of the laser light is hardly affected by the power of the diopter correction lens 57. As a result, the diopter setting can be changed only by changing the diopter correction lens 57. Thereby, the design man-hour in the second objective lens system 50 is reduced. The diopter correction lens 57 does not necessarily have to be located at the turning point P. However, the arrangement on the fundus conjugate plane (that is, the intermediate image L, in other words, the primary enlarged image by the second objective lens system 50) inside the lens attachment 3 should be avoided.

  The second objective lens system 50 forms a turning point Q (second turning point Q) when the lens attachment 3 is mounted. The turning point Q is a point where the laser light (more specifically, the chief ray of the laser light) that has passed the turning point P is further turned along with the operation of the scanning unit 16. The turning point Q is formed at a position optically conjugate with the scanning unit 16 with respect to the second objective lens system 50. The turning point Q is formed on the optical axis L3 of the second objective lens system 50. As shown in FIG. 6, the optical axis L3 of the second objective lens system 50 may be coaxial with the optical axis L1 of the irradiation optical system 10.

  The second objective lens system 50 includes a first lens system 50a and a second lens system 50b. The first lens system 50a in the second objective lens system 50 may have at least a part of the characteristics described above with respect to the first lens system 17a in the first objective lens system 17, and the second objective lens system 50. The second lens system 50b in FIG. 5 may have at least a part of the characteristics described above with respect to the second lens system 17b in the first objective lens system 17.

  In other words, the first lens system 50 a is a main lens system for bending the laser light toward the turning point Q in the second objective lens system 50. That is, the first lens system 50a bends the laser light toward the turning point Q at a position where the chief ray height of the laser light in the second objective lens system 50 is highest. In addition, the first lens system 50 a is arranged closest to the eye to be examined in the second objective lens system 50.

  The first lens system 50 a may be formed by a single lens 51. The lens 51 may be an aspheric lens that suppresses the spherical aberration of the image formed at the turning point Q. The lens surface 51a on the light source side is formed with a curved surface such that the radius of curvature increases as the position is away from the optical axis L3 of the second objective lens system 50 in order to reduce spherical aberration.

  Here, the angle of view of the fundus image and the working distance are in a trade-off relationship. In order to secure a larger working distance while realizing an angle of view of φ90 ° or more, for example, the lens 51 has a curvature radius on the lens surface 51b on the eye side to be examined with respect to a curvature radius on the lens surface 51a on the light source side. It is formed to be large. It was confirmed that the larger the radius of curvature of the lens surface 51b on the eye side, the easier it is to secure the interval w between the lens surface 51b (where the lens surface 51b is closest to the eye side to be examined) and the turning point Q. . In the example of FIG. 6, the lens surface 51b is a flat surface, and its radius of curvature is infinite. Therefore, it is easy to design an optical system that can obtain a sufficient interval w. Thus, as a result of forming the lens surface 51b with a sufficiently large radius of curvature, the working distance is easily secured. Thereby, for example, the examinee or the like can easily open the subject (work for lifting the upper eyelid with a finger or the like). In the design solution of the optical system of FIG. 6 by the inventor, it was possible to secure an interval w of about 13 mm while securing an angle of view of 100 ° or more. Here, assuming that the inspection window is also used by the lens surface 51b, and the working distance is assumed to be a value obtained by subtracting about 3 mm, which is a typical distance from the corneal apex of the human eye to the pupil, from the distance w, the working distance is 10 mm. The degree can be secured. The lens surface 51b may be a curved surface such as a spherical surface. In this case, the radius of curvature of the lens surface 51b is preferably set to a value that is, for example, 10 times or more the desired working distance.

  The second lens system 50b is disposed between the first lens system 50a and the scanning unit 16 (more specifically, between the first objective lens system 17). The second lens system 50b has at least one tilt lens. When the second lens system 50b includes a plurality of lenses, two or more lenses may be tilted lenses, or all may be tilted lenses as shown in FIG.

  The second lens system 50 shown in FIG. 6 includes a cemented lens 52 and convex meniscus lenses 53, 54, and 55 as tilt lenses. As shown in FIG. 6, in each of the inclined lenses 52, 53, 54, and 55, the lens surface on the light source side is larger than the lens surface 51a on the light source side in the first lens system (more specifically, the lens 51). It is formed to have a radius of curvature. Each inclined lens may be a spherical lens. In addition, any of the inclined lenses 52, 53, 54, 55 has a positive power. However, the present invention is not necessarily limited thereto, and an aspherical lens and / or a lens having negative power may be applied to a part or all of the lenses included in the second lens system 50b. . In the second objective lens system 50 as well, as in the first objective lens system 17, the tilt lenses 52, 53, 54 and 55 are arranged between the first lens system 50 a and the scanning unit 16, thereby The reflected light from the lens surface of the one lens system 50a is prevented from entering the light receiving elements 25, 27, and 29.

  The second lens system 50b may include a lens for correcting the aberration generated by the first lens system 50a. For example, the cemented lens 52 corrects chromatic aberration. More specifically, the cemented lens 52 may be an achromatic lens formed by bonding at least two lenses having different light dispersion (Abbe number). In order to suppress reflection on the cemented surface of the cemented lens 52, the refractive indexes of the lenses and the adhesive for bonding the lenses in the cemented lens 52 match each other (including substantially the same). You may do it. Further, each lens included in the cemented lens 52 may be selected so that the power of the cemented lens 52 becomes zero.

  Note that it is not necessary for the cemented lens 52 to correct all chromatic aberrations that occur when the lens attachment 3 is mounted. The lens attachment 3 may further include a chromatic aberration correction lens 59 (achromatic lens) that is not inclined. By using this together, chromatic aberration may be corrected. In this case, it is preferable that the power of the lens 59 is 0 (that is, the sum of the powers of the concave lens and the convex lens is 0).

  The convex meniscus lenses 53, 54, and 55 have positive power. For this reason, it contributes to bending the laser beam to the turning point Q. However, the bending amount is sufficiently smaller than that of the first lens system 50a.

  In the present embodiment, the astigmatic difference (astigmatic difference at the turning point P) caused by the optical scanners 16a and 16b is the tilt lens 172 provided in the first objective lens system 17 disposed in the housing of the SLO1. It is corrected (reduced) by 173. Here, a case where an astigmatic difference caused by the optical scanners 16 a and 16 b remains through the first objective lens system 17 can be considered. When the laser beam incident on the second objective lens system 50 has the above-mentioned astigmatism, the tilt lens included in the second lens system 50b is light so that the astigmatism is in a direction to cancel (reduce) the astigmatism. It may be inclined with respect to the axis L1. For example, as shown in FIG. 6, the tilt amounts of the tilt lenses 52, 53, 54, 55 in the second objective lens system 50 are tilted so as to further reduce the remaining astigmatic difference.

  Further, as shown in FIG. 6, when the second lens system 50b includes a plurality of tilt lenses, some of the tilt lenses and the remaining tilt lenses are connected to the optical axis L3 ( Alternatively, they may be arranged in opposite phases with respect to the optical axis L1) of the irradiation optical system 10. As a specific example, in the second objective lens system 50b of FIG. 6, the inclined lenses 52 and 53 and the inclined lenses 54 and 55 are disposed so as to be inclined in opposite phases with respect to the optical axis L3. As a result, the inclination of the image plane generated by each of the inclined lenses 52 and 53 and the inclined lenses 54 and 55 can be canceled out. It is not always necessary to correct the tilt of the image plane inside the second lens system 50b. For example, the tilt of the image plane generated by the tilt lens of the second lens system 50b may be corrected by tilting the lenses included in the first lens system 50a. In this case, at least one lens included in the first lens system 50a is disposed in the opposite phase with respect to the at least one inclined lens included in the second lens system 50b with respect to the optical axis L3.

<Placement of perforated mirror>
In the above description, the perforated mirror 13 has been described as being disposed at a position conjugate with the anterior segment. In order to more suitably suppress noise light, the perforated mirror 13 may be disposed at the corneal conjugate position when the working distance is appropriate. When the SLO 1 has an aperture unit 230 as shown in FIG. 3 and any one of the scattered light photographing apertures 232 and 233 is disposed in the optical path of the light receiving optical system 20, the apertures 232 and 233 have large openings. Therefore, there may be a case where the apertures 232 and 233 cannot sufficiently remove noise light. In particular, noise light due to corneal reflection is easily guided to the light receiving elements 25, 27, and 29. On the other hand, when the working distance is appropriate, the perforated mirror 13 is arranged at the corneal conjugate position so that the corneal reflection is satisfactorily removed in the perforated mirror 13.

<Light shielding member>
The light shielding unit 22 is provided at a position deviating from the fundus conjugate plane in the optical path between the perforated mirror 13 and the light receiving elements 25, 27, and 29. The light shielding unit 22 transmits light from the fundus conjugate surface and shields at least part of the reflected light from the lens surfaces of the objective lens systems 17 and 50. In the present embodiment, the light shielding unit 22 shields light near the optical axis L2 of the light receiving optical system 20.

  In the present embodiment, the light-shielding portion 22 is a black-spot plate having a black spot 22a that forms a light-shielding area and a light-transmitting plate 22b in which a ring-shaped opening is formed (see FIG. 7). The black spot 22a is disposed on the optical axis L2, for example, and is provided to shield light in the vicinity of the optical axis L2. The translucent plate 22b is formed in a region away from the optical axis L2, and is provided to transmit light from the fundus conjugate surface. Here, the vicinity of the optical axis L2 may be a region close to the optical axis L2 with respect to the outer edge of the light passing region from the fundus that is reflected by the perforated mirror 13. As will be described later, it is more preferable that the black dot 22a is formed in a region near the optical axis L2 with respect to the inner edge of the passage region. A suitable installation range of the black spot 22a will be described later.

  Note that the installation position of the light shielding unit 22 (that is, the position deviated from the fundus conjugate plane) can be defined on the condition that it is at least deviated from the substantially conjugate position of the fundus. That is, the light shielding unit 22 shields light in the vicinity of the optical axis L2 (mainly including light from the lens surface) among the light traveling toward the light receiving elements 25, 27, and 29, and in a region away from the optical axis L2. Pass light (mainly light from the fundus conjugate plane). In this case, the light shielding unit 22 is configured to pass light from a substantially conjugate plane (front and back surfaces with respect to the condensing surface of the fundus).

  Further, the installation position of the light shielding unit 22 may be a position between the pupil conjugate position and the fundus conjugate position, and deviating from both the pupil conjugate position and the fundus conjugate position. For example, as shown in FIGS. 2 and 8, the installation position of the light shielding unit 22 may be between the perforated mirror 13 and the pinhole plate 23. As described above, in the present embodiment, in the lenses 51 and 171 in which the amount of bending of the laser light is relatively large, reflection on the lens surface on the light source side becomes a problem. Therefore, the light shielding unit 22 may be disposed at a position conjugate with the light source side lens surfaces 51a and 171a of the lens 51 or the lens 171. For the sake of convenience, FIG. 8 will be described on the assumption that the light shielding portion 22 is disposed at a position conjugate with the lens surface 171a. However, compared with the lens 171, the lens 51 that bends the laser light more easily causes the reflected light on the light source side lens surface to be guided to the light receiving elements 25, 27, and 29. For this reason, it is more preferable that the light shielding unit 22 is disposed at a conjugate position with the light source side lens surface 51a of the lens 51 (a ray diagram in this case is omitted). Further, one light shielding portion 22 may be arranged at each of the conjugate position of the lens surface 171a and the conjugate position of the lens surface 51.

  The light shielding unit 22 removes reflected light from, for example, the lens surfaces 51a and 171a by shielding the vicinity of the optical axis of the light receiving optical system 20. The image of the laser light irradiation area A on the lens surfaces 51 a and 171 a is formed in the area B near the optical axis of the light receiving optical system 20 at the position of the light shielding portion 22. Here, the irradiation area A is sequentially displaced by scanning with laser light. However, the displacement of the reflected light from the lens surfaces 51 a and 171 a is canceled by passing through the scanning unit 16. As a result, the image of the irradiation area A is formed in a certain area (specifically, in the vicinity of the optical axis L2) at the installation position of the light shielding member 23 conjugate with the lens surface 171a or the lens surface 51a. Is done. That is, when the reflected light from the lens surface 171a or the lens surface 51a is reflected by the perforated mirror 13, the reflected light is incident on the inside of the region B by a conjugate relationship. Therefore, the light-shielding area formed by the black dots 22b is formed in the area B, so that the reflected light from the lens surface 17a is removed.

  Even when there is a slight error between the installation position of the light shielding unit 22 and the conjugate position of the lens surface 171a or the lens surface 51a, the light shielding unit 22 favorably suppresses the reflected light from the lens surface 171a or the lens surface 51a. This inventor confirmed that it was possible by the simulation calculation using the ray tracing method. Therefore, the installation position of the light shielding unit 22 may be arranged away from the front and rear with respect to the conjugate position of the lens surface 171a or the lens surface 51a within a range suitable for the purpose of the present disclosure. When the diopter of the optical system is adjusted by the diopter adjustment unit 40, a deviation may occur between the light shielding unit 22 and the conjugate position of the lens surface 171a or the lens surface 51a, but this deviation can also be allowed.

  The light shielding region (black dot 22) is formed in a range where the viewing angle (apparent size) with respect to the pinhole 23a is equal to the viewing angle of the opening 13a of the perforated mirror 13 at the installation position of the light shielding unit 22. Also good.

  For example, the light-shielding area may be such that the viewing angle with respect to the pinhole 23a at the installation position of the light-shielding part 22 completely coincides with the opening 13a. In this case, reflected light from the lens surface 171a or the lens surface 51a may enter the light receiving elements 25, 27, and 29 while suppressing a decrease in the amount of light from the fundus Er guided to the light receiving elements 25, 27, and 29. It is suppressed. The light shielding area may be formed so that the viewing angle with respect to the pinhole 23a is larger than the viewing angle of the opening 13a within a range that does not completely block the fundus reflection light.

  In the following description, the light shielding unit 22a is described as shielding light in all the wavelength ranges emitted from the laser light emitting unit 11, but is not necessarily limited thereto. For example, a filter that transmits fluorescence from the fundus (mainly part of the visible range) and blocks observation light (mainly infrared light) may be used. In this case, by irradiating the excitation light and the observation light from the laser light emitting unit 11, it is possible to satisfactorily observe the fluorescent fundus image while suppressing the noise light in the observation image. A light-shielding member having a light-shielding part 22a formed of such a filter and a light-shielding member that shields light in all the wavelength ranges emitted from the laser light emitting part 11 are arranged to be switched with respect to the optical axis L2. A unit may be provided in SLO1.

<Polarizing plate>
Further, as illustrated in FIG. 2, the SLO 1 may include a polarization unit 45 in the light receiving optical system 20. The polarization unit 45 includes a polarizing plate 46 (deflection unit) and a drive mechanism 46a. The polarizing plate 46 is inserted into and removed from the optical path between the perforated mirror 13 and the light receiving elements 25, 27, and 29 by driving control of the driving mechanism 46 a. Reflected light from the objective lens system 17 and the second objective lens system 51 is shielded by the deflection plate 46, and the direction of linearly polarized light that can be transmitted through the polarizing plate 46 is adjusted so that light from the fundus is transmitted. . The polarization direction of the reflected light from the objective lens system 17 and the second objective lens system 51 is constant. On the other hand, the photoreceptor cells and the like have anisotropy in the retina of the fundus, and thus the fundus reflection light has a polarization direction different from that of the reflection light from the objective lens system 17 and the second objective lens system 51. For this reason, the polarizing plate 46 can be adjusted so as to meet the above conditions by appropriately rotating (spinning) the polarizing plate 46 around the optical axis L2. Such adjustment work may be performed at the time of product shipment, for example.

<Other Embodiments Regarding Objective Lens System>
As described above, in the present embodiment, the shooting angle of view is switched by attaching and detaching the lens attachment 3. That is, in the present embodiment, the first objective lens system 17 provided in the main body 2 in advance and the second objective lens system 50 provided in the lens attachment 3 are used only through the objective lens system 17. The fundus is photographed with the angle of view. In addition, fundus photographing is performed at a second photographing field angle different from the first photographing field angle through both the objective lens system 17 and the second objective lens system 50. However, the configuration for switching the shooting angle of view is not necessarily limited to the method of the present embodiment. For example, in the objective lens system provided in the main body of the SLO, the photographing field angle may be switched by switching the positional relationship of the lenses. In this case, for example, the positional relationship between the lenses included in the objective lens system may be switched along the optical axis of the irradiation optical system, and thereby the photographing field angle may be switched. Further, the field angle of view may be switched by exchanging the lens attachment attached to the body surface of the main body on the subject side. In this case, the SLO body does not necessarily have an objective lens system. In any of these cases, at least a part of the features described above with respect to the objective lens system 17 or the second objective lens system 50 in the present embodiment is applicable. In this case, in any embodiment, at least a part of the irradiation optical system 10 and at least a part of the light receiving optical system 20 are accommodated in the same casing.

<Control system configuration>
Next, the control system of SLO1 will be described with reference to FIG. In SLO1, each part is controlled by the control unit 70. The control unit 70 is a processing device (processor) having an electronic circuit that performs control processing of each unit of the SLO1 and arithmetic processing. The control unit 70 is realized by a CPU (Central Processing Unit), a memory, and the like. The control unit 70 is electrically connected to the storage unit 71 via a bus or the like. The control unit 70 is also electrically connected to the laser beam emitting unit 11, the light receiving elements 25, 27, and 29, the drive mechanisms 14 a and 46 a, the scanning unit 16, the input interface 75, and the monitor 80.

  The storage unit 71 stores various control programs, fixed data, and the like. The storage unit 71 may store temporary data or the like. The photographed image by SLO1 may be stored in the storage unit 71 as shown in FIG. However, the present invention is not necessarily limited to this, and the captured image may be stored in an external storage device (for example, a storage device connected to the control unit 70 via a LAN and a WAN).

  For convenience, in the present embodiment, the control unit 70 is also used as an image processing unit. For example, the control unit 70 forms a fundus image based on the light reception signals output from the light receiving elements 25, 27, and 29. Further, image processing (image processing, analysis, etc.) for the fundus image is also performed by the control unit 70. Of course, the image processing unit may be a separate device from the control unit 70. As shown in FIG. 9, the control unit 70, based on signals from the respective light receiving elements 25, 27, 29, displays a maximum of three types of images based on the signals from the respective light receiving elements 25, 27, 29. Generate almost simultaneously.

  Further, the control unit 70 controls each of the above members based on an operation signal output from the input interface 75 (operation input unit). The input interface 75 is an operation input unit that accepts an examiner's operation. For example, a mouse and a keyboard may be used.

<Description of operation>
Due to the above-described characteristics of the optical system, it is possible to reduce the reflected image of the reflected light from the objective lens system 17 and the second objective lens system 50 from appearing in the fundus image. However, since the effect of suppressing the reflection and the amount of light from the fundus Er guided to the light receiving elements 25, 27, and 29 are in a trade-off relationship, the effects from the objective lens system 17 and the second objective lens system 50 are Design solutions and photographing conditions that allow reflection of the reflected image are also conceivable. Therefore, in this embodiment, the reflection of the reflected image is reduced by image processing.

  First, an overview of processing performed in the control unit 70 of the present disclosure will be described. The control unit 70 performs fundus image shooting processing, and acquires the fundus image as a shot image by shooting the fundus Er. In addition, the control unit 70 acquires a background image (also referred to as a “mask image”) for the captured image (fundus image). The “background image” includes at least a reflection image by the objective lens system. The background image is an image in which at least a reflection image by the objective lens system is captured so that the eye to be inspected is not captured. In addition, the background image is used for comparison with an observation image (a fundus image in the present embodiment) with a background difference which is a kind of image processing (see FIG. 12). In addition to the reflected image of the objective lens system, the background image includes artifacts that hinder observation and analysis of the fundus image.

  Such a background image may be acquired based on photographing by the photographing optical system in the “light shielding state”. The “light shielding state” is realized by shielding the eye to be examined of a lens that generates a reflected image in the objective lens system. In an objective lens system having a plurality of lenses, it is desirable that light is shielded at a position on the eye side of a lens that generates a target reflected image. For example, the light may be shielded at the position of the lens barrel tip of the objective lens system. In this case, the reflection image resulting from all the lenses of the objective optical system can be included in the background image. The timing of capturing the background image may be before or after capturing the fundus image to be subjected to background difference (details will be described later).

  The objective lens system may be shielded from light by disposing a “light shielding member” closer to the eye to be examined than a lens that generates a reflected image. The light blocking member is arranged on the optical path of the illumination light, thereby blocking the illumination light guided to the eye to be examined. The light shielding member may be a separate member from the apparatus main body, or may be provided in advance in the apparatus main body. Specifically, a lens cap, a shutter, a dark curtain, etc. can be applied as the light shielding member. In the case of a shutter, the drive mechanism (shutter mechanism) that inserts and removes the shutter (light-shielding member) with respect to the optical path of the illumination light is an apparatus main body or an objective lens barrel (for example, a lens attachment barrel). May be provided. The shutter mechanism includes a closed state in which a subject eye side of a lens that generates a reflected image is shielded by the light shielding member in accordance with insertion / removal of the light shielding member, and a subject eye side of the lens that generates the reflected image is shielded by the light shielding member. Switch between open states, not done. The shutter mechanism may be a mechanism that switches between a state in which the front end of the lens barrel of the objective lens system is covered with a light shielding member and a state in which the lid is removed. The surface of the light shielding member that is irradiated with illumination light is preferably formed of a material having a high absorption rate of illumination light. For example, black flocked paper may be used. In addition, for example, a new material using carbon nanotubes has attracted attention in recent years, and this may be applied.

  Further, the light shielding state by the light shielding member may be detected by a sensor or the like. The background image may be captured (acquired) based on the detection result of the light shielding state. For example, when a shutter mechanism is provided, a background image may be taken based on switching from an open state to a closed state of the shutter mechanism.

  In the present embodiment, the background difference based on the fundus image (see FIG. 11) and the background image (see FIG. 12) is performed by the control unit 70, thereby suppressing the influence of the reflected image by the objective lens system in the fundus image. The obtained image is generated as a difference image (see FIG. 13). In other words, the reflection of the reflected image on the fundus image by the objective lens system is reduced afterwards by image processing. The difference image in the present embodiment may be a difference image generated by directly taking the difference between the fundus image and the background image. Further, it may be a difference image generated by performing correction on at least one of the fundus image and the background image and taking a difference between the corrected images.

  Here, in the difference image obtained as a result of the background difference, random noise may increase as compared with the original fundus image. Thus, for example, the control unit 70 may acquire a difference image for each of a plurality of fundus images obtained by shooting the same region at different timings, and generate an addition average image based on each difference image. As a result, a front image of the fundus in which random noise is suppressed can be obtained together with a reflected image by the objective lens system.

  Further, for example, a case where a resonant scanner is applied to the scanning unit of the irradiation optical system can be considered. In the resonant scanner, the scanning of the laser beam may become unstable due to disturbance or the like. For this reason, there is a possibility that the magnification in the scanning direction in at least a part of the image differs between the fundus image and the background image. As a result, there may be a case where the appearance position of the artifact is shifted between the fundus image and the background image. If the position of minute artifacts due to dust or the like adhering to the optical system of SLO1 is shifted between the fundus image and the background image, the minute artifacts are increased by performing the background difference. It is possible.

  On the other hand, the control unit 70 extracts a portion including the reflection image by the objective lens system from the background image and extracts it (for convenience, the “partial background image”, for example, the region U in FIG. 14). The difference image may be acquired by performing background difference based on the fundus image. That is, the difference image is generated by subtracting the luminance value in the partial background image for each pixel from the region corresponding to the position of the partial background image in the fundus image. As a result, a minute artifact is suppressed to the same level as the original fundus image, and a fundus front image in which the influence of the reflected image by the objective lens system is suppressed is generated as a difference image (see, for example, FIG. 15). . Further, the processing time in the image processing can be shortened compared to the case where the background difference using the entire background image is performed.

  Here, in the fundus image and the background image, the position of the region where the reflected image is generated by the objective lens system is substantially constant. For example, it occurs in the center of the image. For this reason, the partial background image may be an image obtained by extracting a region at a predetermined position in the background image. Further, the control unit 70 may detect a region of the reflected image by the objective lens system from the background image and extract a partial background image from the detected region.

  By the way, in order to satisfactorily reduce the reflected image by the objective lens system, it is preferable that the photographing conditions of the fundus image and the background image are the same. Alternatively, it is preferable to suppress the influence due to the difference in photographing conditions by performing image correction on one or both of the fundus image and the background image. The photographing condition is a condition (for example, a set value) relating to at least one of the output of illumination light, the gain of the light reception signal, and the diopter in the photographing optical system.

  In order to make the shooting conditions coincide with each other, for example, the control unit 70 may shoot a background image without changing (receiving) the shooting conditions after shooting the fundus image that is the target of the background difference. . In this case, the fundus image and the background image are acquired in a series of shooting operations.

  In addition, the control unit 70 may store information indicating imaging conditions when capturing the fundus image in the storage unit in association with the fundus image. Then, the control unit 70 may capture the background image by reproducing the imaging conditions stored in the storage unit. In this case, a good background image can be obtained in performing the background difference from the fundus image even if the shooting conditions are once reset or changed after the fundus image is shot.

  The control unit 70 also blocks a plurality of background images with different shooting conditions while switching shooting conditions regarding at least one of the output of illumination light, the gain of the received light signal, and the diopter of the shooting optical system. You may acquire beforehand by repeating imaging | photography with. In this case, a background image serving as a background difference from the fundus image is selected from a plurality of background images acquired in advance. For example, the control unit 70 may select a background image acquired under the imaging condition that is the same as or closer to the imaging condition of the fundus image. A background difference between the selected background image and the fundus image is performed, and a difference image is obtained. In this case, the differential image in which the reflected image by the objective lens system is satisfactorily suppressed can be obtained immediately after the fundus image is captured (for example, with a slight time lag from the fundus image capture). In this method, for example, an observation image of a fundus image is sequentially acquired, and a difference image based on each fundus image is sequentially generated and displayed, so that a real-time moving image based on the difference image can be displayed.

  Here, the output characteristics of the light source, the gain characteristics of the light receiving element, and the like may change gradually over time. The background image is preferably updated as appropriate. For example, the background image may be updated periodically every few days (including every few weeks, every few months, etc.). Further, the update time may be managed, and the control unit 70 may display guide information for informing the background image update on the monitor when the predetermined update time is approached.

  Next, an example of a technique for performing image correction on one or both of the fundus image and the background image will be described. For example, the control unit 70 may acquire in advance at least one background image when the imaging condition relating to at least one of the output of illumination light and the gain of the received light signal is the first imaging condition. . When the imaging condition (second imaging condition) in the fundus image that is the target of the background difference is different from the first imaging condition in the background image, the control unit 70 determines the contrast in at least one of the fundus image and the background image or The brightness may be corrected, and the background difference may be performed based on the corrected image. In this case, the correction amount in image correction (that is, matching) related to contrast or brightness may be acquired according to information indicating the first shooting condition and information indicating the second shooting condition. For example, the correction value may be acquired by a calculation result of a predetermined calculation formula that is a function of information indicating the first shooting condition and information indicating the second shooting condition. Further, the correction value may be acquired by referring to a lookup table in which the correction value is associated with each combination of information indicating the first shooting condition and information indicating the second shooting condition. Good. For example, the contrast and brightness correction amounts for correcting the background image in the first shooting condition to the background image in the second shooting condition are the same as the background image in the first shooting condition and the second shooting condition. You may obtain | require from the difference with a background image. In this case, the correction value stored in the lookup table can be obtained based on, for example, a plurality of background images with different shooting conditions. In this method, a large number of background images may not be stored in advance in the storage unit. Also, with this method, a good differential image can be obtained immediately after the fundus image is captured. For this reason, for example, a real-time moving image based on the difference image can be displayed.

  In this method, a plurality of images having different shooting conditions (second shooting conditions) regarding at least one of the output of illumination light and the gain of the received light signal may be used as a background image acquired in advance. . A background image photographed under a second photographing condition closer to the photographing condition of the fundus image (first photographing condition) is selected from a plurality of backgrounds having different photographing conditions. Then, the contrast or brightness in at least one of the fundus image and the background image is corrected with a correction value corresponding to the information indicating the first shooting condition and the information indicating the second shooting condition, and the corrected image The background difference may be performed based on the above. In this case, the correction value may be used to interpolate a difference in shooting conditions between a plurality of background images. As a result, the number of background images acquired in advance can be suppressed. Further, since there are changes over time such as the output characteristics of the light source and the gain characteristics of the light receiving element, the correction value and the background image may be updated as appropriate.

  Photographed with fundus image (referred to as “first fundus image”) taken with fundus reflected light of the first illumination light and fundus reflected light with second illumination light (wavelength range different from the first illumination light) Even when at least two images of the fundus image (referred to as “second fundus image”) are combined, the background difference can be applied. “Combination” may be processing for generating one image by mixing colors corresponding to each image for each corresponding pixel in at least two images.

  For example, a background image in the first wavelength range (referred to as “first background image”) and a background image in the second wavelength range (referred to as “second background image”) may be acquired. Then, the background difference between the first fundus image and the first background image, the background difference between the second fundus image and the second difference image are respectively performed, and the first difference image and the second difference image are generated, and the first difference is generated. A synthesized difference image may be obtained by synthesizing the image and the second difference image. It is conceivable that the reflected image in the objective lens system is generated with a different intensity distribution and range for each wavelength range. For this reason, the background difference is performed for each fundus image in each wavelength region, so that the reflected image of the objective lens system is preferably suppressed in the first difference image and the second difference image. Since such images are synthesized, a good synthesized difference image can be obtained.

  However, it is not always necessary to perform the background difference for each fundus image in each wavelength region. For example, the composite difference image may be obtained by a background difference based on the first composite image of the first fundus image and the second fundus image and the second composite image of the first background image and the second background image. Good. Further, a difference image may be generated by a fundus image and a background image having different wavelength ranges of illumination light, or a composite image using such difference images may be generated.

  Next, a specific operation in SLO1 will be described with reference to the flowchart shown in FIG. After the alignment (S1) between the eye to be examined and the apparatus is completed, the imaging mode is selected by the control unit 70 (S2). For example, a plurality of shooting modes corresponding to the shooting method and the angle of view may be prepared in advance. For example, in the present embodiment, the shooting mode is roughly divided into a “normal mode” that is a shooting mode when the lens attachment 3 is not attached and a “wide-angle mode” that is a shooting mode when the lens attachment 3 is attached. Is done. That is, the “wide-angle mode” has a larger shooting angle of view than the “normal mode”. Each of the “normal mode” and the “wide-angle mode” further includes a mode for photographing a fundus image by fundus reflection light (more specifically, an “IR mode” for infrared imaging). , And “color mode” for color photography) and a mode for photographing a fundus image by fluorescence emitted from the fundus (more specifically, “ICG mode” for ICG photography, FAG photography) For example, “FA mode” for spontaneous fluorescence photography, etc.) may be prepared. These shooting modes may be selected in accordance with, for example, a shooting mode selection operation on the input interface 75. Further, the control unit 70 may automatically select the shooting mode based on the detection result of the state of the apparatus and / or according to a predetermined shooting order. In this case, for example, in response to a signal from the sensor 8 (see FIG. 1) indicating whether or not the lens attachment 3 is attached, the control unit 70 selects “normal mode” or “wide angle mode”. May be.

  In accordance with the selected imaging mode, the control unit 70 uses at least the wavelength range of the laser beam from the laser beam emitting unit 11 and the light receiving element used for observing and photographing the fundus image among the three light receiving elements 25, 27, and 29. The setting of the photographing optical system (the irradiation optical system 10 and the light receiving optical system 20) is switched (S3).

  Next, the control unit 70 determines whether or not a specific shooting mode is selected (S4). The specific photographing mode here is a mode for photographing using fundus reflection light. For example, “IR mode”, “color mode”, and the like. In the present embodiment, the wavelength range of the excitation light (that is, the objective light) in the case of fluorescence imaging using filters (for example, dichroic mirrors 31 and 32; other filters not shown) may be provided in the light separation unit 30 and the like. Light in the wavelength range of the reflected light from the lens system 17 and the second objective lens system 50 is less likely to be incident on the light receiving element for obtaining a fluorescent image. For this reason, in the captured image, the above reflection is unlikely to be a problem. However, even in the fluorescence image, a reflection image due to reflection by the objective lens system 17 and the second objective lens system 50 may occur. For this reason, the background difference may be performed on the fluorescent image. In this case, it is preferable that the background difference and the background image captured under the same imaging conditions as when the fundus is captured with fluorescence are performed. For example, in a configuration in which an exciter filter and a barrier filter are inserted into the optical path of the photographing optical system at the time of fluorescent photographing, the background image may be acquired by photographing under conditions in which the filters are similarly arranged. In addition, for example, when the above-mentioned reflection is a problem only in the “wide-angle mode” between the “normal mode” and the “wide-angle mode”, the “wide-angle mode” is defined as the condition of the specific shooting mode. May be.

  In the case of the specific shooting mode (S4: Yes), the control unit 70 limits at least one adjustment range of the light amount and the gain (S5). For example, in the adjustment range, in the fundus image and the background image to be described later, the luminance value of a region (for example, the central portion of the fundus image) in which the reflected image of the objective lens system 17 and the second objective lens system 50 is reflected is saturated ( Limited to the range that does not saturate. This is because when the luminance value is saturated, the area does not include information indicating the structure of the fundus. Such an adjustment range may be set, for example, based on a result of an experiment or the like in advance, or may be set based on an observation image. Note that “restriction of the adjustment range” means that the adjustment range is narrower in the SLO1 shooting modes compared to shooting modes other than the specific shooting mode. It also includes switching to a value (fixed value) at least one of the light amount and the gain.

  Next, a fundus image is taken (S6). For example, in the “color mode”, a color fundus image is taken. The laser light emitting unit 11 emits light in the red, green, and blue wavelength ranges simultaneously (may be emitted in order at different timings), and based on the signals from the light receiving elements 25, 27, and 29, red, A reflection image based on light in the green and blue wavelength ranges is formed. Then, a color fundus image is formed by combining these reflection images (see FIG. 11). The color fundus image obtained in this way may be stored in the storage unit 71.

  Next, in the present embodiment, a background image is taken (S7). The background image includes artifacts that hinder observation and analysis in the fundus image. In this embodiment, a typical artifact is the reflected image S by the objective lens systems 17a and 51a. Also, images such as dust attached to the optical system, scratches, dirt, and flares on the optical system can be included in the background image as artifacts. In SLO, reflection of the edge of an optical scanner such as a galvanometer mirror may occur as an artifact. In FIG. 12, a dust image D is shown as an example.

  The background image may be, for example, an SLO image that is captured while being shielded from light at the position of the eye E and the lens surface (for example, the lens surface 51a and the lens surface 171a) disposed closest to the eye E. . In “light shielding”, a light shielding member is arranged between the lens surface 51a (or lens surface 171a) closest to the eye E and the eye E so that the fundus is not reflected in the SLO image taken as the background image. That may be realized. The light shielding member is not necessarily provided in advance in the apparatus. For example, a lens cap, a shutter, a dark curtain, etc. can be applied as the light shielding member. The shutter mechanism may be provided in the main body of the SLO 1 or the lens attachment 3, and in this case, the shutter mechanism lowers the light by blocking the shutter at the rear stage (the side away from the light source) of the lens 51 and the lens 171.

  Moreover, it is not always necessary to realize light shielding by arranging the light shielding member at the position of the lens surface 51a (or the lens surface 171a). For example, when the eyelid of the eye E is closed, the fundus Er is not captured in the SLO image. Therefore, it can also be considered that light shielding is performed by closing the subject's heel. In this case, for example, the control unit 70 may detect a blink of the eye to be examined and take a background image while the eyelid is closed by the blink.

  Note that the background image may be captured by detecting that the light is shielded and using the detection as a trigger (in other words, based on the detection signal). Specifically, for example, a sensor for detecting that the position of the lens surface closest to the eye to be examined is shielded from light may be provided in the main body of the lens attachment 3, and / or SLO1. Based on the signal from the sensor, the control unit 70 may identify whether or not the light is shielded. Moreover, if it is a blink, you may detect based on the imaging | photography result of the anterior eye part with the anterior eye part camera which is not shown in figure, and may detect based on the histogram etc. of an observation image. However, the background image may not be automatically captured when the light shielding state is detected. For example, when the examiner confirms the light shielding and inputs a predetermined operation to the input interface 75, A background image may be taken based on the input.

  In the process of S7, after the fundus image is captured in S6, the fundus image is acquired in S6 for the imaging conditions regarding the output (light quantity) of the light source, the gains of the light receiving elements 25, 27, and 29, and the diopter of the optical system. Shooting in a light-shielded state is performed without changing from time to time. As a result of such shooting, a background image is acquired.

  Next, the control unit 70 acquires a difference image based on the background difference based on the fundus image and the background image (S8). In the difference image, the influence of the artifact on the fundus image is suppressed. For example, as shown in FIG. 13, an image obtained by removing the reflection image S by the objective lens systems 17a and 51a and the image D such as dust from the fundus image of FIG. 11 is acquired as a difference image. The acquired difference image may be stored in the storage unit 71. Further, it may be displayed on the monitor 75. Thus, the reflection of the reflected image by the objective lens system in the fundus image is reduced afterwards by the image processing.

  In the process of S8, contrast adjustment of the difference image may be performed together with the background difference. For example, the correction processing for adjusting the contrast so that the histogram of the intermediate image (a kind of difference image) obtained by the background difference is expanded in a predetermined gradation range is included in the processing of S8. Also good.

  Here, the difference image after contrast adjustment is expressed by the first number of gradations (for example, 8 bits). The first number of gradations may be the number of gradations when displayed on the monitor 75. On the other hand, SLO1 may acquire an image expressed by a second number of gradations (for example, 12 bits) larger than the first number of gradations by the processes of S6 and S7. That is, both the fundus image and the background image that are subject to background difference may be expressed by the second number of gradations. And the control part 70 performs the background difference of the images expressed with the 2nd gradation number, and acquires an intermediate image (a kind of difference image). And after performing contrast adjustment with respect to an intermediate image, the image after contrast adjustment may be compressed and the difference image expressed with the 1st gradation number may be acquired. In this way, artifacts can be removed with higher accuracy.

  In this embodiment, in order to obtain a difference image, a background image and a fundus having the same image capturing conditions (that is, image capturing conditions regarding the output of the light source, the gains of the light receiving elements 25, 27, and 29, and the diopter of the optical system) are the same. A background difference is performed based on the image. Since the photographing conditions are the same, it is difficult for the artifact components reflected in the background image and the fundus image to differ. For this reason, the influence of the artifact in the difference image is easily suppressed.

  Note that the above-described image processing such as background difference can be appropriately applied to an SLO having a refractive system (lens system) in the objective optical system. However, as described above, when the luminance value of the reflected image S is saturated in the fundus image, information on the fundus at the position of the reflected image S is obtained in the difference image as a result of removing the artifact by the background difference. It is possible that there is not. In order to suppress the saturation of the luminance value in the reflected image S, the feature for suppressing reflection of reflected light from the objective lens system 17 and the second objective lens system 50 shown in the present embodiment is shown. Of these, at least one may be used in combination with image processing as appropriate.

  Further, the above-described image processing such as background difference is not limited to application to SLO, and other than that, “the objective lens system including at least one lens and the illumination light emitted from the light source are described above. An imaging optical system including: an irradiation optical system that irradiates an eye to be examined via an objective lens system; and a light receiving optical system that includes a light receiving element that receives reflected light of the illumination light from the eye to be examined via the objective lens system, And an ophthalmologic imaging apparatus that generates a captured image based on a signal from a light receiving element ” Such an ophthalmologic photographing apparatus may be a fundus photographing apparatus. In this case, illumination light is irradiated to the fundus of the eye to be examined by the irradiation optical system, and fundus reflection light of the illumination light is received by the light receiving element by the light receiving optical system. As a fundus imaging apparatus other than SLO, for example, a fundus camera may be considered. Further, the ophthalmologic photographing apparatus may be an anterior ocular segment photographing apparatus.

  As mentioned above, although it demonstrated based on embodiment, when implementing this indication, the content of embodiment can be changed suitably.

1 SLO
DESCRIPTION OF SYMBOLS 3 Lens attachment 10 Irradiation optical system 11 Laser light emission part 16 Scan part 16a, 16b Optical scanner 17 Objective lens system 20 Light reception optical system 25,27,29 Light receiving element 50 2nd objective lens system 51,171 Aspherical lenses 52,172 Joint lens 171a, 172a, 172b Lens surface Er Fundus L1, L3 Optical axis P, Q Turning point

Claims (14)

A scanning unit for scanning a laser beam emitted from a light source on the fundus of the eye to be examined, and a laser beam arranged between the eye to be examined and the scanning unit, and the laser beam guided from the scanning unit operates the scanning unit An objective lens system that forms a turning point that is turned along with the irradiation optical system, and
A scanning laser ophthalmoscope comprising the objective lens system in common with the irradiation optical system, and a light receiving optical system having a light receiving element that receives light from the fundus upon irradiation of the laser light,
The objective lens system includes a first lens system for bending the laser light toward the turning point, and a second lens system disposed between the first lens system and the scanning unit,
The second lens system includes an inclined lens arranged to be inclined with respect to the optical axis of the irradiation optical system, and the lens surface on the light source side of the inclined lens is the light source side of the first lens system. Scanning laser ophthalmoscope with a larger radius of curvature than the lens surface.   The scanning laser ophthalmoscope according to claim 1, wherein the second lens system corrects an aberration caused by the first lens system. The light source emits at least a laser beam having a first wavelength and a laser beam having a second wavelength different from the first wavelength;
3. The scanning laser ophthalmoscope according to claim 2, wherein the second lens system includes a cemented lens that corrects chromatic aberration generated in the first lens system with respect to at least the laser light having the first wavelength and the laser light having the second wavelength.   4. The scanning laser ophthalmoscope according to claim 3, wherein the plurality of lenses further included in the cemented lens and the refractive index of the adhesive for joining the plurality of lenses have the same value.   The scanning laser ophthalmoscope according to any one of claims 1 to 4, wherein the first lens system is arranged so that an optical axis thereof is along an optical axis of the irradiation optical system.   The first lens system includes at least one lens arranged to be inclined with respect to the optical axis of the irradiation optical system so as to cancel the inclination of the image plane on the fundus conjugate plane caused by the inclined lens. The scanning laser ophthalmoscope according to any one of claims 1 to 5.   7. The first lens system according to claim 1, wherein the first lens system is an aspheric lens that suppresses spherical aberration of image formation at the turning point by forming at least one lens surface in an aspheric shape. The scanning laser ophthalmoscope according to any one of the above.   Of the intermediate image plane of the fundus formed by the objective lens system, the second lens system is between the intermediate image plane formed closest to the first lens system and the first lens system. The scanning laser ophthalmoscope according to claim 1, wherein the scanning laser ophthalmoscope is disposed. The scanning unit includes two optical scanners that are arranged at different positions and have different scanning directions of the laser light,
The tilt lens is disposed to be inclined with respect to the optical axis of the irradiation optical system so as to cancel out the astigmatism at the turning point caused by the two optical scanners. The scanning laser ophthalmoscope according to any one of 8. A housing that houses at least a part of the irradiation optical system and at least a part of the light receiving optical system;
A lens attachment to be attached to the subject-side casing surface,
The scanning laser ophthalmoscope according to claim 1, wherein the objective lens system is provided in the lens attachment. A housing that houses at least a part of the irradiation optical system and at least a part of the light receiving optical system;
A lens attachment that switches a field angle of view in accordance with attachment to and detachment from a subject-side housing surface, and directs laser light incident through the objective lens system to a second turning point different from the turning point A lens attachment having a second objective lens system that bends
The scanning according to any one of claims 1 to 8, wherein the second objective lens system includes at least one second inclined lens arranged to be inclined with respect to the optical axis. Type laser ophthalmoscope. The scanning unit includes two optical scanners that are arranged at different positions and have different scanning directions of the laser light,
The second inclined lens is disposed to be inclined with respect to the optical axis of the irradiation optical system or the second objective lens system so that the astigmatic difference remaining at the second turning point is canceled. Item 12. A scanning laser ophthalmoscope according to Item 11.   The scanning laser detection according to claim 11 or 12, wherein the wide-angle lens attachment includes at least two inclined lenses arranged in opposite phases with respect to the optical axis so as to cancel out the inclination of the image plane in the fundus conjugate plane. glasses. A scanning unit for scanning a laser beam emitted from a light source on the fundus of the eye to be examined, and a laser beam arranged between the eye to be examined and the scanning unit, and the laser beam guided from the scanning unit operates the scanning unit An objective lens system that forms a turning point that is turned along with the irradiation optical system, and
A scanning laser ophthalmoscope comprising the objective lens system in common with the irradiation optical system, and a light receiving optical system having a light receiving element that receives light from the fundus upon irradiation of the laser light,
The scanning unit includes two optical scanners that are arranged at different positions and have different scanning directions of the laser light,
The objective lens system includes a first lens system for bending the laser light toward the turning point, and a second lens system disposed between the first lens system and the scanning unit,
The second lens system includes an inclined lens arranged to be inclined with respect to the optical axis of the irradiation optical system, and the inclined lens is an astigmatic difference at the turning point caused by the two optical scanners. A scanning laser ophthalmoscope characterized by being arranged so as to be inclined with respect to the optical axis of the irradiation optical system so as to be in a direction to cancel out the light.